Year Percent 2002 38.62789 2003 37.41886 2004 29.72107 2005 31.11485 2006 28.63597 2007 30.10501 2008 24.89227 2009 29.2975 2010 26.21007 2011 23.74366 2012 24.39087 2013 22.81066 2014 22.13704 2015 20.63432 2016 25.74031 2017 26.4202 2018 22.0429 2019 25.77397 2020 29.97558 2021 33.59762